Abstract: The luminescence of lanthanide ions is based on f-f transitions. Due to the core nature of the 4f orbitals involved in the process, as well as the forbidden nature of these transitions, the emission properties make these ions uniquely suited for a variety of applications involving light emission, such as lighting, imaging, and sensing. Since the f-f transitions are forbidden, the emission is most efficiently promoted through coordinated chromophores. The use of these coordinated ligands provides unique opportunities. They can be functionalized to tailor the chemical and photophysical properties of the resulting complexes.1 We have used this approach to synthesize complexes that can be used as imaging agents for cancer cells.2 By extending the conjugation of the ligand we shifted the excitation wavelengths into the visible and isolated complexes that can be used as molecular nanothermometers.3 In addition, we used carbazole-based ligands that enabled excitation of the resulting complexes in the biological window by a two-photon process. Finally, we used oligothiophene-based ligands to isolate complexes that luminesce and generate singlet oxygen. These compounds have shown appreciable phototoxicity when incubated with HeLa cell.
In this presentation, I will discuss my group’s recent work on lanthanide ion complexes with dual activity, as well as some recent results on unusual coordination chemistry4-5 of these fascinating metal ions.
Figure 1. Temperature-dependent emission spectrum of K3[Tb(dipicCbz)3]. Inset shows the intensity of the 5D4 ® 7F5
transition as a function of temperature.3
1. Luminescence of Lanthanide Ions in Coordination Compounds and Nanomaterials. de Bettencourt-Dias, A., Ed. John Wiley and Sons: 2014.
2. Monteiro, J. H. S. K.; Machado, D.; de Hollanda, L. M.; Lancellotti, M.; Sigoli, F. A.; de Bettencourt-Dias, A., Selective Cytotoxicity and Luminescence Imaging of Cancer Cells with A Dipicolinato-based EuIII Complex Chem. Commun. 2017, 53, 11818-11821.
3. Monteiro, J. H. S. K.; Sigoli, F. A.; de Bettencourt-Dias, A., A Water-soluble TbIII complex as temperaturesensitive luminescent probe. Can. J. Chem. 2018, 96, 859-864.
4. de Bettencourt-Dias, A.; Beeler, R. M.; Zimmerman, J. R., Anion-π and H-Bonding Interactions Supporting Encapsulation of [Ln(NO3)6/5]3-/2- (Ln=Nd,Er) with a Triazine-based Ligand. J. Am. Chem. Soc. 2019, 141, 15102-15110.
5. de Bettencourt-Dias, A.; Beeler, R. M.; Zimmerman, J. R., Secondary-Sphere Chlorolanthanide(III) Complexes with a 1,3,5-Triazine-Based Ligand Supported by Anion-p, p-p, and Hydrogen-Bonding Interactions. Inorg. Chem. 2020, 59, 151-160.